1895.] The Mouth-Parts of the Lepidoptera. 551 
flap, composed of a firmer basal region and a more delicate, 
membranous, distal region, the whole organ bearing many 
tactile hairs. It overlies the mouth-parts, extending beyond 
the mandibles and out over the fleshy labium (see figs. 3 and 
5, lb., plate XXV). This condition of the labrum is radically 
different from that presented by this organ among the Frenate, 
the more specialized Lepidoptera (see postea). 
The long 5- to 6-segmented maxillary palpi of Micropteryx 
already pointed out in‘ Walter’s admirable study of the 
maxillary palpi in the Lepidoptera as an indication of the 
generalized character of the mouth-parts of this genus, are 
very like, in point of number of segments and general habitus, 
the maxillary palpi of the Trichoptera. The maxille and 
labium in general characters are also similar in the two 
groups. The matter of mandibles is of special interest. In 
certain species of Micropteryx they are present as functional or- 
gans, although the tendency toward their reduction is fully 
displayed within the limits of the genus; in Trichoptera func- 
tional mandibles have not yet been found, although the dis- 
tinct rudiments of mandibles are present. Manifestly now, as 
the tendency of specialization in both groups is toward a reduc- 
tion to complete atrophy of the mandibles, the Jugatee can not 
be looked upon asin any way lineal descendents of the Trichop- 
tera. The affinity of the two groups must be of the character 
of two dichotomously divided lines of descent, diverging from 
a racial type which possessed conditions of mouth-parts, wing- 
venation, wing-clothing, and thoracic structure of a character 
suggested by the present conditions of these organs presented 
by the generalized members of the two groups. 
The question of the presence or absence of rudimentary man- 
dibles among the Trichoptera has been a bone of contention 
for insect morphologists, though it seems pretty obvious that 
if a sufficient number of species be examined both conditions 
4 Walter A., Palpus maxillaris Lepidopterorum, in Jen. Zeitsch. f. Naturwiss. 
v. 18, 1884. In this study Walter found that the maxillary palpi appear in a 
general series of lepidopterous forms from lowest moths to highest butterflies in 
a progressive state of reduction, 6-segmented in Micropteryx, entirely reduced 
among the Nymphalidae. 
